Contributions to Industrial-Minerals Research

U.S. Department of the Interior

U.S. Geological Survey

Bulletin 2209–H

Stratiform Barite Deposits in the Roberts Mountains 

Allochthon, Nevada: A Review of Potential Analogs 

in Modern Sea-Floor Environments

Chapter H of
Contributions to Industrial-Minerals Research

James D. Bliss, Phillip R. Moyle, and Keith R. Long, Editors

Bulletin 2209–H

U.S. Department of the Interior

U.S. Geological Survey 

Stratiform Barite Deposits in the Roberts Mountains 

Allochthon, Nevada: A Review of Potential Analogs 

in Modern Sea-Floor Environments

By Randolph A. Koski and James R. Hein

Chapter H of
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

Version 1.0, 2003

This publication is available only online at:

http://pubs.usgs.gov/bul/b2209-H/

Manuscript approved for publication, January 9, 2004

Layout by Stephen L. Scott

Text edited by George A. Havach

Any use of trade, product, or firm names in this publication

is for descriptive purposes only and does not imply 

endorsement by the U.S. Government 
Contents

Abstract------------------------------------------------------------------------------------------------------ 1

Introduction -------------------------------------------------------------------------------------------------- 1

Stratiform Barite Deposits of Nevada -------------------------------------------------------------------- 2

 Regional Geology -------------------------------------------------------------------------------------- 2

 Deposit Characteristics ------------------------------------------------------------------------------- 3

 Regional Tectonic Models for the Roberts Mountains Allochton -------------------------------- 3

 Depositional Models for Stratiform Barite ---------------------------------------------------------- 5

Modern Ocean-Floor Barite Deposits -------------------------------------------------------------------- 7

 Disseminated Barite ----------------------------------------------------------------------------------- 7

 Diagenetic Barite Deposits --------------------------------------------------------------------------- 9

 Subsurface Deposits Related to Zones of Sulfate Reduction ------------------------------- 9

 Focused Flow: Cold-Seep Barite Deposits --------------------------------------------------- 11

 Hydrothermal Barite Deposits ----------------------------------------------------------------------- 12

Modern Marine Barite Deposits as Analogs of Statiform Barite Deposits in Nevada: 

A Starting Point --------------------------------------------------------------------------------------------- 13 

 Tectonic Setting --------------------------------------------------------------------------------------- 13 

 Depositional Processes ------------------------------------------------------------------------------ 14

 Working Hypothesis and Avenues for Future Research ----------------------------------------- 14

Acknowledgments ----------------------------------------------------------------------------------------- 15

References Cited ------------------------------------------------------------------------------------------- 15

Figures

1. Sketch map of Nevada, showing distribution of massive barite deposits within

 the Roberts Mountains Allochthon -------------------------------------------------------------- 2

2. Photographs illustrating characteristics of massive barite deposits ------------------------------ 4

3. Schematic models for barite deposition in Paleozoic continental-margin settings ------------- 5

4. Two process-oriented models for deposition of massive barite deposits ------------------------ 6

5. Relief map of the Pacific Ocean showing location of diagenetic (subsurface and

 cold seep) and hydrothermal barite deposits --------------------------------------------------- 8

6. Plot of estimated productivity (as carbon flux) versus barite-accumulation rate 

 in sediment cores from three north-south transects across the Equator ------------------- 9

7. Pore-water profiles for dissolved barium and sulfate in two sediment cores from

 the Peru continental margin ---------------------------------------------------------------------- 9

8. Photographs of massive barite deposits associated with cold seeps and 

 hydrothermal vents ------------------------------------------------------------------------------- 10

Table

1. Setting and characteristics of barite deposits in Nevada and on the modern 

 sea floor --------------------------------------------------------------------------------------------- 8

III
1

Abstract

The United States is a net importer of barite, a critical 

mineral for the oil and gas industry; more than 80 percent 

of current domestic consumption of barite is imported from 

China. Nearly all of the domestic production of barite comes 

from stratiform deposits in Nevada. The “modern analogs” 

approach adopted in this review can contribute to improving deposit models and the long-term resource picture in the 

United States.

Massive barite deposits in Nevada are interlayered with 

deep-water siliceous sedimentary strata of Paleozoic age 

within the Roberts Mountains Allochthon. Although the barite 

deposits formed along the long-lived, tectonically active 

margin of western North America before the Antler orogeny, 

uncertainty still exists regarding key aspects of their genesis, 

especially with respect to tectonic setting and depositional 

processes. Proposed tectonic settings include a continental 

slope adjacent to an ocean basin, and a rifted basin formed 

on continental crust. A margin dominated by other stress configurations and strike-slip faulting may also have been present 

during the Paleozoic. Hypotheses for the genesis of sedimenthosted, stratiform barite deposits in Nevada can be grouped 

into two categories: (1) a synsedimentary hydrothermal model 

and (2) an ocean-circulation/productivity-zone model. Both 

models include a stage involving bacterial reduction of seawater sulfate.

Disseminated, diagenetic, and hydrothermal barite deposits are widespread features of the modern ocean. In the Pacific 

Ocean, disseminated barite deposits (max 9 weight percent 

BaSO4) are forming below high-productivity zones (for 

example, in equatorial belts) and on the flanks of ocean ridges 

(as fallout of “black smoker” particles). Massive barite deposits of diagenetic (in the subsea floor and at cold seeps) and 

hydrothermal origins are present in several sediment-covered 

tectonic settings, including ocean ridges (Escanaba Trough 

and Guaymas Basin), oceanic transform faults (Blanco Fracture Zone), marginal basins (Sea of Okhotsk), convergent 

margins (Peru, Oregon, Alaska), and transform margins (California Continental Borderland). Both hydrothermal and diagenetic barite deposits may be present in some environments 

(for example, the California California Borderland).

On the basis of a consideration of tectonic settings and 

a comparison of deposit attributes (associated rock types, 

size, structure), mineralogy (BaSO4 content, SiO2 content), 

and geochemistry (S- and Sr-isotopic ratios) for modern and 

ancient massive barite deposits, cold seeps along transform 

margins (or, possibly, marginal basins) represent the most 

promising present-day metallogenetic analogs for stratiform 

barite. Hydrothermal systems can also produce high-grade 

barite, but the ubiquity of associated sulfide mineralization on 

the modern sea floor (and the paucity of sulfides in Nevada 

deposits) is problematic. On the basis of data from modern 

barite deposits, the presence of vent-specific faunas (tubeworms) and the variation in δ34S values for barite (related to 

bacterial reduction of seawater sulfate) may not permit discrimination between a diagenetic or hydrothermal origin for 

ancient barite deposits.

Introduction

Barite (BaSO4) is a critically important mineral for the 

energy industry. Since 1975, about 90 percent of the barite 

consumed worldwide has been used in the oil and gas industry. In 2001, 95 percent of the barite produced and sold in 

the United States was used as a weighting agent in gas- and 

oil-well-drilling fluids. The estimated U.S. consumption of 

barite in 2001 was 2.96 million t, of which 2.7 million t was 

imported; between 1997 and 2002, 86 percent of imported 

barite came from China (Searls, 2003). In the decades ahead, 

the barite market will continue to be governed by oil- and 

gas-drilling activity (Bearden, 1997). The increasing U.S. 

energy demand, coupled with renewed emphasis on domestic production, should result in increased domestic oil and 

gas exploration both onshore and offshore. An increasing 

Stratiform Barite Deposits in the Roberts Mountains 

Allochthon, Nevada: A Review of Potential Analogs 

in Modern Sea-Floor Environments

 Introduction

By Randolph A. Koski and James R. Hein
2 Contributions to Industrial-Minerals Research

demand for natural gas, for example, will require a doubling 

of the number of gas wells drilled annually by the year 2020 

(Anonymous, 2001). Thus, the national need for barite and 

other energy-related industrial commodities is expected to 

rise commensurately.

Most of the barite mined in the United States comes from 

Nevada. As a result, the United States is the third-largest producer of barite in the world, after China and India. Approximately 435,000 t of barite was shipped from three Nevada 

mines in 2000; considerably smaller amounts were mined in 

Georgia and Tennessee (Searls, 2000). High overland-shipping costs for processed barite ore have led to a decline in 

U.S. production, especially for barite produced at the Nevada 

sites, which are distant from markets in North America. Current U.S. reserves of barite are approximately 26 million t 

(Searls, 2003).

Barite mined in Nevada is recovered from stratiform 

deposits in the Roberts Mountains Allochthon, a well-defined 

northeast-trending belt of sedimentary and volcanic rocks of 

Paleozoic age; more than 120 individual deposits are known 

(fig. 1; Papke, 1984). The deposits are widely distributed as 

conformable layers and lenses of massive barite interbedded 

with predominantly siliceous sedimentary strata, most notably 

chert.

Although sedimentary barite deposits in Nevada and 

elsewhere have been the focus of considerable research 

(for example, Hanor, 2002), uncertainty still exists regarding key aspects of their genesis, especially tectonic setting 

and mineral-forming processes. Although the tectonic setting is generally characterized as “continental margin,” little 

agreement exists regarding the details of plate interaction or 

faulting that promoted barite mineralization. With respect to 

mineral-forming processes, two general hypotheses have been 

proposed: (1) a synsedimentary hydrothermal model and (2) 

an ocean-circulation/productivity-zone model. Both of these 

process-oriented models are consistent with the distribution 

of deposits within a continental-margin setting.

Recent discoveries of barite deposits forming in diverse 

submarine environments of tectonically active continental 

margins can shed light on the origins of the stratiform deposits found in the geologic record. Sediment-floored, continental-margin settings that host massive barite mineralization 

include ocean ridges, rifted continental margins, marginal 

basins, transform margins, and trench-slope environments of 

convergent margins. In this chapter, we adopt a “modern analogs” approach—a consideration of the tectonic setting and 

geochemical characteristics of sea-floor barite deposits—to 

enhance our understanding of the occurrence and genesis of 

Paleozoic stratiform barite deposits in Nevada and elsewhere 

in the North American Cordillera. In following this approach, 

we make no prior assumption that an unequivocal modern 

analog exists in any strict sense. This chapter, therefore, represents a starting point. Our ultimate goal is improved deposit 

models that can contribute to the long-term barite resource 

picture in the United States. In addition, new insights into 

barite metallogenesis may be applied to other types of mineral 

deposits formed in continental-margin settings (for example, 

gold, phosphorite).

Stratiform Barite Deposits of Nevada

Regional Geology

Stratiform barite deposits in Nevada are concordant 

within siliceous sedimentary strata of the Roberts Mountains 

Allochthon, an assemblage of deformed Cambrian through 

Devonian eugeoclinal strata extending from southeastern 

California northeastward across Nevada into Idaho (fig. 1). 

These displaced and deformed rocks were thrust as much as 

200 km eastward over carbonate-shelf rocks of the adjacent 

continental margin along the Roberts Mountains thrust during 

the Antler orogeny in Late Devonian through Early Mississippian time (Roberts and others, 1958; Johnson and Pendergast, 

1981; Madrid and others, 1992).

Sedimentary- and volcanic-rock types within the Roberts 

Mountains Allochthon include chert, shale, argillite, quartzite, 

quartz- and feldspar-rich sandstone, basalt, limestone, sili0 50 100 KILOMETERS

Figure 1. Sketch map of Nevada, showing distribution of massive barite deposits (blue areas) within the Roberts Mountains 

Allochthon (after Papke, 1984). Eastern margin of the allochthon is 

marked by thrust-fault pattern, with teeth on upper plate.
3

ceous carbonates, and phosphorite. This lithologic association 

is generally considered to represent both hemipelagic and 

turbiditic deposition within a spectrum of continental rise, 

slope, and basin environments during the evolution from a 

passive to an active margin (Madrid and others, 1992; Finney 

and others, 1993). During the Antler orogeny, these rocks 

were stacked in a sequence of nappes, resulting in an olderover-younger stratigraphy. Stratiform barite deposits are most 

abundant in Ordovician and Devonian sedimentary rocks 

but also occur in rocks of Cambrian and Silurian age (Poole, 

1988). Dubé (1988) reported a Famennian age (Late Devonian) for brachiopods in barite and similar ages for radiolarians in chert from several districts in the Roberts Mountains 

Allochthon.

Deposit Characteristics

Detailed geologic descriptions of Nevada barite deposits 

are presented in numerous publications (for example, Shawe 

and others, 1969; Papke, 1984; Dubé, 1988; Poole, 1988), 

and so only a brief summary is given here and in table 1. 

Individual barite beds typically are 0.3 to 15 m thick (fig. 

2A), but aggregate thicknesses (excluding thin interbeds of 

chert or shale) may exceed 25 m (Papke, 1984). Maximum 

strike lengths for individual barite beds are about 100 m but 

for thicker aggregate deposits may exceed 300 m. Barite 

deposits are closely associated with bedded radiolarian chert 

(fig. 2B) and, to a lesser extent, with shale and argillite, which 

occur as thin interbeds in both barite and chert. Less common 

sedimentary-rock types that occur in barite deposits include 

limestone, siltstone, and conglomerate containing chert or 

barite fragments. In places, massive and clastic barite beds are 

interstratified. Although igneous rocks are generally a minor 

component of the Roberts Mountains Allochthon, greenstone 

(alkalic basalt) and lamprophyre dikes are present in some 

districts (Dubé, 1988; Madrid and others, 1992). Deposits 

pinch out against other rock types or are terminated by syndepositional high-angle faults.

Within deposits, massive saccharoidal and laminated 

barite are most abundant (fig. 2). Poole (1988) listed three 

other types of stratiform barite: dense concentrations of spheroidal masses (rosettes) in beds of fine-grained barite, chert, 

and shale; barite conglomerate and sandstone; and barite 

cement in sandstone and siltstone.

Quartz is ubiquitous in laminated and spheroidal barite 

beds, whereas calcite, pyrite, witherite, and celestite are 

reported in only a few deposits (Papke, 1984). Organic 

matter, which is a major impurity (several weight percent) 

in both bedded barite and associated chert, is mostly marine 

sapropel (Poole and Claypool, 1984). Phosphatic nodules 

and lenses occur in laminated and rosette barite, as well as in 

associated chert beds, in the Toquima Range (Rye and others, 

1978; Graber and Chafetz, 1990; Coles, 1996). According to 

Papke (1984), powdery masses of Fe and Mn oxides, as well 

as Fe-rich gossans derived from sulfide oxidation, occur in 

about 25 and 33 percent of the deposits, respectively. These 

small oxide-rich bodies are generally oriented parallel to bedding. We note, however, that massive sulfide deposits are not 

spatially associated with stratiform barite mineralization in 

Nevada.

An important discovery with relevance to the genesis 

of barite deposits is the preservation in barite beds of fossil 

brachiopod shells and tubeworms (fig. 2D) that appear to 

represent macrofaunas endemic to fluid ventsites on the sea 

floor during periods of barite deposition (Dubé, 1988; Poole, 

1988).

Regional Tectonic Models for the Roberts 

Mountains Allochthon

The depositional history and tectonic setting for sedimentary rocks of the Roberts Mountains Allochthon have been 

widely debated, and detailed studies of barite deposits have 

contributed to the debate. Most workers believe that the sedimentary strata of the allochthon (including stratiform barite 

deposits) represent a deep-water marine assemblage deposited within a long-lived, tectonically active zone outboard 

(westward) of the continental shelf. This tectonically active 

continental margin may have existed for a period of 135–180 

m.y. before the Antler orogeny (Madrid and others, 1992). 

The Late Devonian (Famennian) age of interbedded barite 

and chert deposits (for example, in the Toquima Range; Dubé, 

1988) suggests that some barite mineralization in outercontinental-margin environments was synchronous with the 

earliest stages of Antler-style tectonism and initial eastward 

emplacement of the Roberts Mountains Allochthon over miogeoclinal-shelf rocks.

Two proposed tectonic settings for sedimentation and 

barite deposition in the Roberts Mountains Allochthon are 

illustrated in figure 3. In the first model (fig. 3A), organic- and 

silica-rich sedimentary strata and barite deposits formed on 

the outer edge of a passive continental margin, outboard of 

the continental shelf underlain by carbonate rocks to the east 

and inboard of a narrow ocean basin and a volcanic arc to the 

west (Maynard and Okita, 1991). The volcanic arc is underlain by a west-dipping subduction zone. According to this 

interpretation, the sedimentary strata and barite deposits were 

emplaced eastward onto the continental margin during plate 

convergence and closure of the ocean basin in Late Devonian 

time.

In the second model (fig. 3B), sedimentation occurred 

in rift basins formed on continental crust (Turner and others, 

1989; Madrid and others, 1992; Finney and others, 1993). 

Similar epicontinental rifts are the proposed settings for 

stratiform Pb-Zn sulfide±barite (sedex) deposits of Paleozoic age in the Canadian Cordillera (Goodfellow and others, 

1993). In this model, detritus entering the basins from terrestrial sources to the east mixed with sand from emergent highlands to the west. The barite-chert-phosphorite association 

developed during periods of minimal clastic sedimentation 

in the rift basins. The occurrence of alkaline basalt records 

multiple episodes of extension and attenuation of continental 

 Stratiform Barite Deposits of Nevada
4 Contributions to Industrial-Minerals Research

crust during Middle Cambrian through Late Devonian time 

(Madrid and others, 1992). Evidence for the formation of true 

oceanic crust in these marginal basins is absent; however, 

scattered tectonized ultramafic bodies in the allochthon may 

represent displaced pieces of asthenosphere (Poole and Desborough, 1973).

Sedimentary basins may have formed under other stress 

configurations in a long-lived complex margin. For example, 

analysis of the distribution patterns of Proterozoic rocks in the 

northern Canadian Cordillera led Eisbacher (1983) to propose 

that much of the western North American continental margin 

during the Middle Paleozoic was dominated by sinistral 

faulting. In that type of setting, pullapart basins could have 

formed by transtensional faulting. Furthermore, Dubé (1988) 

suggested that lamprophyric intrusions in the allochthon may 

represent igneous activity during extension in a transform setting.

Although compositional variations in clastic sedimentary 

units in the Roberts Mountains Allochthon led to suggestions that the assemblage is an exotic terrane (Coney and 

A B

D

C

Figure 2. Characteristics of massive barite deposits. A, Massive barite bed within the Slaven Chert, eastern Northumberland Canyon, 

Nev. B, Trench exposing steeply dipping, bedded barite (gray) and chert (reddish brown) in the Upper Devonian Los Pozos Formation, 

central Sonora, Mexico. C, Sample of massive to thinly laminated barite from the Slaven Chert, Queen Lode Mine, Nev. Darker laminae 

are enriched in organic matter. D, Dense cluster of tubeworms in barite deposit within the Slaven Chert. Photographs courtesy of F.G. 

Poole.
5

others, 1980; Schweickert and Snyder, 1981), analyses of 

stratigraphic relations across the allochthon and recent U-Pb 

data for detrital zircons from sandstone units in the allochthon indicate that detrital sources were exclusive to the North 

American craton (Madrid, 1992; Gehrels and others, 2000).

Depositional Models for Stratiform Barite

Hypotheses for the genesis of sediment-hosted, stratiform 

barite deposits in Nevada fall into two distinct categories: (1) 

formation by synsedimentary hydrothermal processes (Papke, 

Black shale

Continental 

crust

Chert + barite

Outer continental margin Volcanic arc

Oceanic crust

Continental crust

Miogeocline (shelf)

Harmony Platform

Ordovician through Devonian 

sedimentary strata and barite deposits

?

Oceanic crust Alkali basalt

B

A

Figure 3. Schematic models for barite deposition in Paleozoic continental-margin settings. A, Barite is deposited along with chert 

and black shale on outer continental margin, with a narrow ocean basin and island-arc assemblage to the west. Modified from 

Maynard and Okita (1991). B, Barite is deposited within rifted continental margin underlain by sediment derived from continental 

shelf to the east and an elevated platform to the west. Alkalic basalt represents occasional periods of extension and magmatism 

within basin. Curved arrows denote sediment transport; straight arrows denote extension of continental margin. Modified from 

Madrid and others (1992).

 Stratiform Barite Deposits of Nevada
6 Contributions to Industrial-Minerals Research

Carbonate 

platform

Bedded barite

deposits

Sulfate-reduction

zone

Surface barite 

 production

Upwelling

nutrients

Bottom 

currents

Oxic

Anoxic

"Black smoker" plume

"White smoker" 

plume

Barite

deposits

Sulfide

deposits

Synsedimentary

fault

Clastic

sedimentary

Feeder strata

zones

B

A

Figure 4. Two process-oriented models for formation of massive barite deposits. A, Hydrothermal model, in 

which thermal activity within a stratified basin results in proximal massive sulfide and distal massive barite 

deposits. Dissolved barium from hydrothermal vent fluids is concentrated in anoxic bottom waters. Barite 

deposits form where boundary between reduced, H2S-bearing anoxic layer and oxic, sulfate-rich seawater 

intersects basin margins. Source of barium in this model is underlying sedimentary rocks or continental 

crust. Modified from Hanor and Baria (1977). B, Productivity-stratified ocean model, in which upwelling 

along continental margin results in high productivity and barite crystallization in decaying organic matter 

settling to ocean floor. Barite dissolves in anoxic bottom waters and reprecipitates at the oxic/anoxic-water 

boundary. Source of barium in this model is seawater. Modified from Jewell and Stallard (1991) and Jewell 

(1994).
7

1984; Murchey and others, 1987; Dubé, 1988; Poole, 1988; 

Maynard and Okita, 1991) and (2) formation in zones of ocean 

upwelling and high productivity (Graber and Chafetz, 1990; 

Jewell and Stallard, 1991; Jewell, 1994, 2000). Evidence 

cited in support of a synsedimentary hydrothermal origin for 

Nevada barite deposits includes S- and O-isotopic characteristics, lensoid deposits spatially associated with synsedimentary 

block faulting, local Mn-rich zones and Fe-rich gossans, association with mafic volcanic rocks, and the presence of such 

chemosynthetic vent fauna as bivalves and tubeworms. Indirect evidence is the spatial and temporal association of bedded 

barite deposits with sedex Pb-Zn deposits in Paleozoic strata 

of the Canadian Cordillera (Goodfellow and others, 1993).

A synsedimentary hydrothermal or “exhalative” model for 

the formation of hydrothermal barite deposits is illustrated in 

figure 4A. In this model, barium is leached from the underlying sediment by circulating, reduced brines and is transported 

along synsedimentary normal faults to the sea floor, where 

mixing of the brines with seawater induces precipitation of 

barite. Although many S-isotopic ratios for samples of bedded 

barite from Nevada are similar to those of Middle Paleozoic 

seawater sulfate (δ34S=∼25 permil), higher ratios (max 56 

permil) for barite rosettes and concretions indicate that anaerobic reduction of seawater sulfate by bacteria in a closed system 

must have played a role in barite mineralization on the sea 

floor (Rye and others, 1978). The S-isotopic characteristics of 

barite and the occurrence of massive barite in organic-rich sedimentary sections are consistent with hydrothermal deposition 

in anoxic oceanic environments (Turner, 1992b; Poole and 

Emsbo, 2000). The formation of sulfide deposits in this model 

is hypothetical for Nevada barite deposits but is consistent 

with the relation of stratiform barite to Pb-Zn sulfide deposits 

in the Canadian Cordillera (Goodfellow and others, 1993).

An origin for Nevada barite deposits related to ocean 

circulation, upwelling, and high productivity is based on 

87Sr/86Sr ratios, high P and organic-C contents, the presence 

of phosphatic nodules, and the abundance of microfossils in 

barite deposits and associated sedimentary strata (for example, 

the Slaven Chert). The appropriate conditions for barite 

mineralization are fostered by coastal upwelling of oxygendepleted and nutrient-enriched seawater at topographically 

steep segments of continental-margin basins (fig. 4B). The 

resulting “rain” of abundant planktonic debris causes barite 

to precipitate in the upper part of the water column (Bishop, 

1988). The barite then dissolves in sulfate-reducing bottom 

waters and reprecipitates where the bottom waters mix with 

normal sulfate-rich seawater. The modern Andean margin of 

South America is cited as a potential contemporary analog for 

these “biological precipitates” (Jewell, 2000). In this model, 

the source of barium is seawater, and the ore fluid is modified 

seawater that contains no hydrothermal component.

Modern Ocean-Floor Barite Deposits

Barite mineralization occurs in various tectonic settings 

on the ocean floor. Deposits in sedimentary environments 

can be subdivided into disseminated, diagenetic, and hydrothermal types on the basis of various physical and chemical 

attributes (table 1). The locations of known diagenetic and 

hydrothermal barite deposits are shown in figure 5.

Disseminated Barite

In modern ocean basins, barite is widely disseminated in 

sediment and is a minor but ubiquitous particulate phase in 

the water column (Church, 1979; Dehairs and others, 1980). 

The modern oceans, as a whole, are undersaturated with 

respect to barite (Church and Wolgemuth, 1972), although 

saturation conditions exist regionally in the surface, intermediate, and deep waters of some oceans (Monnin and others, 

1999). The BaSO4 content of deep-sea sediment is positively 

related to strong upwelling and high productivity (fig. 6). 

High-latitude regions, the equatorial zone, and continental 

margins of the Pacific Ocean contain anomalous concentrations of barite. The BaSO4 content of biosiliceous sediment 

in continental-margin and high-latitude regions and of biocarbonate sediment in equatorial regions may reach 9 weight 

percent on an opal- or carbonate-free basis (table 1; Arrhenius 

and Bonatti, 1965). Fossil deposits of low-grade disseminated 

barite occur in many continental-margin sequences in the geologic record in which a history of upwelling is also evident 

(Stamatakis and Hein, 1993).

Although the specific mechanism for barite precipitation in the water column of high-productivity zones has not 

yet been determined, Dehairs and others (1980) and Bishop 

(1988) proposed that barite is formed in microenvironments 

within the upper part of the water column which contain 

decaying organic matter. More recently, Bertram and Cowen 

(1997) identified three morphologic types of barite (ovoid, 

hexagonal, and microcrystalline) in the surface oceans and 

suggested that precipitation occurred by both biogenic and 

abiogenic processes. The most abundant form of barite related 

to upwelling, referred to by many workers as “marine barite,” 

is characterized by small grain size (<5 μm), an ellipsoidal 

morphology similar to the ovoid type of Bertram and Cowen 

(1997), and present-day seawater Sr- and S-isotopic ratios 

(Paytan and others, 1993, 2002).

The vigorous hydrothermal systems and buoyant plumes 

along oceanic spreading axes are another source of barite in 

sediment. Well-crystallized barite particles have been identified as a minor constituent of “black smoker” vent fluids emanating from the Juan de Fuca Ridge and the East Pacific Rise 

(Feely and others, 1987; Mottl and McConachy, 1990), and 

barite particles have been recovered from distal vent plumes 

2 km from active discharge sites (Dymond and Roth, 1988). 

Bostrom and others (1973) and Dymond (1981) demonstrated 

that deep-sea sediment on the flanks of the East Pacific Rise 

and in the adjacent Bauer Deep are enriched in Ba to about 

7 weight percent on a carbonate-free basis. Sediment near 

ocean ridges probably contains plume-derived barite, as well 

as barite derived from biogenic and hydrogenous sources. 

Barite crystals collected from hydrothermal plumes are 

 Modern Ocean-Floor Barite Deposits
8 Contributions to Industrial-Minerals Research

Sea-floor deposits

Characteristic Nevada deposits

Disseminated Diagenetic,

subsurface

Diagenetic,

cold seep Hydrothermal

Tectonic setting -------------------- Active continental margin ------ Flanks of ocean ridges,

high latitudes, and

equatorial belts.

Convergent m argins------------- Convergent and transform m argins, m arginal basins, and p assive

margins.

Ocean ridges near or intersecting continental

margins, and transform

margins.

BaSO4 content (in weight

percent); other m inerals.

>90; quartz, mi ca, calcite,

pyrite

<10; siliceous sediment------- 10-50, m ax 80 in sma ll deposits; siliceous.>90; trace pyrite. <50–>90; sulfides, silica,

manganese oxide.

Crystal size and form------------- Individual crystals, m ax 1 mm

across; m icrocrystalline to

spheroidal, rosette.

<100 μm, ovoid or m icrocrystalline (biogenic);

euhedral (hydrothermal).

<1 mm, needles, bladed,

tabular.

20–700 μm; bladed, rosette.Coarse grained (max 2 c m

diam), euhedral, rosette.

Sr content in barite (in

weight percent).

Max 0 .5 Max 1 8 (ovoid) n.d. .5-11 Max ∼3

δ34S value of barite relative

to SW .

SW to >SW SW >SW to >>SW >SW SW to >>SW

87Sr/86Sr ratio o f barite relative to SW.

SW to >SW SW >SW <SW to >SW <SW

Associated megafauna?---------- Yes No No Yes Yes

Table 1. Setting and characteristics of barite deposits in Nevada and on the modern sea floor.

[Data for Nevada deposits from Rye and others (1978), Papke (1984), Poole (1988), and Maynard and others (1995); data for sea-floor deposits from Feely and others 

(1987), Peter and Scott (1991), Peter and Shanks (1992), Dia and others (1993), Goodfellow and Franklin (1993), Zierenberg and others (1993), Fu and others (1994), 

Koski and others (1994), Torres and others (1996a, b, 2002), Aquilina and others (1997), Bertram and Cowen (1997), Naehr and others (2000), Greinert and others 

(2002), Hein (2002), and Paytan and others (2002). N.d., no data; SW, seawater]

Hydrothermal

Cold seep

Subsurface diagenetic

EXPLANATION

Guaymas Basin

California 

Continental

Borderland

Monterey Canyon

Escanaba Trough

Mariana Trough

Japan Sea

Sea of Okhotsk

Peru Margin

Oregon Continental Margin

Aleutian Forearc

Lau Basin

Woodlark Basin

Gulf of Mexico

Blanco Fracture Zone

Izu-Bonin Arc

Figure 5. Relief map of the Pacific Ocean, showing locations of diagenetic (subsurface and cold seep) and hydrothermal barite deposits. Locations of diagenetic sites from Dia and others (1993), Torres and others (1996a, b, 2002), Aquilina and others (1997), Naehr and 

others (2000), and Greinert and others (2002); locations of hydrothermal sites from Koski and others (1988), Peter and Scott (1988), Moore 

and Stakes (1990), Urabe and Kusakabe (1990), Binns and others (1993), Astakhova and Mel’nichenko (2002), and Hein (2002). Locations 

of deposits in passive-margin setting of the Gulf of Mexico (Fu and others, 1994) are also shown. Only deposits in sediment-floored 

environments of the Pacific rim are described in text.
9

coarser (20–70 μm) than those of other marine barites, and 

have well-formed bladed or rosette morphologies (Feely and 

others, 1987; Paytan and others, 2002). Plume barite crystals 

have Sr-isotopic ratios between those for contemporaneous seawater sulfate and basaltic Sr-isotopic ratios, whereas 

S-isotopic ratios are either comparable to seawater sulfate 

or slightly lower owing to the presence of reduced sulfur of 

hydrothermal origin (Paytan and others, 2002).

Diagenetic Barite Deposits

Diagenetic barite deposits form just beneath the sea floor, 

on the ocean floor at the margins of sulfate-reducing zones in 

bottom waters, and on the ocean floor in areas of cold-seep 

exhalations (fig. 5; table 1).

Subsurface Deposits Related to Zones of Sulfate 

Reduction

After burial, disseminated barite from the water column 

dissolves (or partially dissolves) during bacterial sulfate 

reduction. The breakdown of barite and the consequent 

release of barium into ambient pore water are linked to the 

anaerobic degradation of organic matter in the sediment. 

Additional barium in pore water is supplied from decaying 

organic matter, and barium may also be derived from interaction of circulating fluids with basalt and other crustal rocks at 

depth. Barite is redeposited along diagenetic fronts at which 

reduced fluids mix with oxic pore waters in the subsurface or 

with oxygenated seawater at the sea-floor/seawater interface 

(fig. 7; Torres and others, 1996a). The migration of Ba-rich 

fluids can result from compaction, seismic activity, sudden 

mass-wasting events, and advection of subsurface brines. All 

of these processes are common in areas of strong oceanic 

upwelling at subduction margins (both compressional and 

extensional) and where large submarine fans span the continental margin. Sulfur fractionation during bacterial sulfate 

reduction results in barite with δ34S values higher than those 

of seawater (Torres and others, 1996b; Paytan and others, 

2002).

Barite accumulations formed at diagenetic fronts will 

remain small and low grade if the sedimentation rate does 

not vary and fluids are not advected (Torres and others, 

1996a, b). Larger, higher grade barite deposits (max 50 

weight percent BaSO4 ) can form, however, at diagenetic 

fronts when sedimentation rates decline suddenly or when 

advection of fluids occurs that contain sulfate from deeper 

parts of the sedimentary section (Torres and others, 1996b). 

Ocean-floor barite concretions may have formed where the 

zone of sulfate reduction occurs immediately beneath the sea 

floor. Barite concretions collected from near-surface marine 

mud are porous, spherical to tabular masses with smooth to 

rough and knobby surfaces (for example, Revelle and Emery, 

1951); the deposits are as much as 0.5 m across and contain 

as much as 80 weight percent BaSO4 mixed with host sediment. Analogous barite concretions in pelagic sedimentary 

sequences in the geologic record are attributed to diagenetic 

remobilization of barium and precipitation of barite at the 

sea-floor/seawater boundary during pauses in sedimentation 

(Bréhéret and Brumsack, 2000).

1 2 3 4 5 6

1000

200

0

400

800

600

1200

0

Equatorial

12° from the Equator

BARITE-ACCUMULATION RATE,

IN MICROGRAMS OF BASO4 PER

SQUARE CENTIMETER PER YEAR

ESTIMATED PRODUCTIVITY,

IN MILLIGRAMS OF CARBON

PER SQUARE METER PER DAY

Figure 6. Estimated productivity (as carbon flux) versus barite-accumulation rate in sediment cores from three north-south 

transects across the Equator. Data from Paytan and others 

(1996).

Diatomaceous mud

Diatomaceous mud

200

100

0

0 200 400 0 400 800

0 10 20 30 0 2 4

400

300

200

100

0

500

Barite

deposit

Barite

deposit

600

Ba CONCENTRATION, IN MICROMOLES PER LITER

SO4 CONCENTRATION, IN MILLIMOLES PER LITER

DEPTH, IN METERS

A B

2-

Figure 7. Pore-water profiles for dissolved barium (squares) and sulfate (dots) in two sediment cores from Ocean Drilling Program sites 

685 (A) and 688 (B) on the Peru continental margin (von Breymann 

and others, 1990; Torres and others, 1996b). Barite deposits form along 

diagenetic “fronts” as barium mobilized in zones of sulfate reduction 

at depth reprecipitates under sulfate-stable, oxic conditions closer to 

sea floor.

 Modern Ocean-Floor Barite Deposits
10 Contributions to Industrial-Minerals Research

5 cm

Mn coating Mn coating

5 cm

A

C

E F

B

D

Figure 8. Massive barite deposits associated with cold seeps and hydrothermal vents. A, Mounds of massive porous barite 

constructed at cold-seep site on unconsolidated sediment in the Derugin Basin, Sea of Okhotsk. Mounds are as much as 

10 m high. Field of view, about 1.2 m across. Photograph from Greinert and others (2002). B, Small barite mounds covered 

with vestimentiferan tubeworms at cold seep in Monterey Canyon offshore central California. Field of view, about 0.5 m 

across. Photograph from Naehr and others (2000). C, Porous massive barite with layered appearance and manganese 

coating from the Sea of Okhotsk. Photograph from Greinert and others (2002). D, Knobby massive barite chimneys (with 

white rims on broken cross sections in upper half of photograph) on platform of massive sulfide on sediment-covered floor 

of the Escanaba Trough, southern Gorda Ridge. Cluster of barite chimneys is about 1 m high. Photograph from Koski and 

others (1994). E, Nearly pure barite with coating of manganese oxide from chimney in the Escanaba Trough. F, Massive 

barite dredged from the California Continental Borderland contains fossilized worm-tube structures and is interpreted to be 

hydrothermal in origin (Hein, 2002).
11

Barite may be deposited directly on the sea floor where 

sulfate-reducing bottom waters are present in the modern 

oceans. These conditions are restricted to organic-rich ocean 

basins, such as the Black Sea, the Cariaco Trench, and certain 

fiords (Falkner and others, 1993), and to continental slopes 

where intense upwelling occurs (for example, the Peru-Chile 

margin; Jewell and Stallard, 1991). In local basins within 

these environments, barite particles from the upper part of the 

water column are dissolved in reduced bottom waters. Barite 

subsequently reprecipitates along chemical gradients between 

the reduced Ba-rich waters and normal seawater. Although 

this type of deposit appears to be restricted along modern 

continental margins, it was probably more important in the 

past when regional and global oceanic anoxia was predominant (Jewell, 2000). A key factor in barite deposition on the 

sea floor in such an environment is a low input of terrigenous 

and carbonate sediment; this factor also explains why the 

accumulation of barite is rare even in the few places where 

ocean-floor sulfate reduction occurs today. Furthermore, to 

produce a barite deposit of significant size, the sulfate-reducing bottom waters must remain stable for long periods of 

time, possibly 104–105 years.

Focused Flow: Cold-Seep Barite Deposits

Massive barite deposits in the form of concretions, crusts, 

mounds, and chimneys accumulate around cold seeps in 

various active tectonic settings, including convergent zones, 

marginal basins, and rifted and strike-slip continental margins (fig. 5; table 1). Massive barite deposits have also been 

described in the Gulf of Mexico, a passive-margin setting (Fu 

and others, 1994). This type of diagenetic barite deposit forms 

during the focused discharge (or, at least, localized flow) of 

cold Ba-rich fluids onto the ocean floor and is a manifestation 

of the processes described for the formation of subsurface 

barite in the previous section. Water depths of known deposits 

range from several hundred meters to as much as 3,800 m. 

Relatively large massive barite deposits may result: chimneys 

and mounds from the southern California margin and the Sea 

of Okhotsk (fig. 8A) are reported to exceed 10 m in height and 

to occur intermittently along fault scarps for more than 3 km 

(Lonsdale, 1979; Greinert and others, 2002; Torres and others, 

2002). The Sea of Okhotsk cold-seep vent field covers an area 

of at least 32 km2 (Greinert and others, 2002). High concentrations of methane and hydrogen sulfide characterize the vent 

fluids at some ventsites (Barry and others, 1996; Greinert and 

others, 2002), and cold seeps support unique biologic communities (fig. 8B), including vestimentiferan tubeworms, mussels, 

bryozoans, crinoids, bacterial mats, and other vent-specific 

faunas (Torres and others, 1996a; Aquilina and others, 1997; 

Naehr and others, 2000; Greinert and others, 2002). Minute 

cold-seep barite grains may be transported away from the 

ventsites by bottom currents and added to sediment distributed 

over a wide area (Torres and others, 2002).

Cold-seep barite deposits are characteristically porous, 

with a banded or layered structure indicating multiple episodes or an intermittent style of venting (fig. 8C). Although 

sedimentation rates are commonly high in areas of cold 

seeps, barite deposits generally are nearly pure (>90 weight 

percent BaSO4). Minor amounts of pyrite are associated with 

some deposits (Fu and others, 1994; Greinert and others, 

2002). S-isotopic ratios of cold-seep barites generally exceed 

those for contemporary seawater sulfate. Barites from these 

environments vary in Sr content (max 11 weight percent) and 

Sr-isotopic ratio, depending on the rock types leached by circulating fluids. Evidently, the distribution of cold-seep barite 

mineralization along convergent and transform continental 

margins is related to fault zones or scarps that crosscut previously buried sedimentary strata. Thus, the low-temperature 

fluid seeps associated with barite deposition on the Peru convergent margin appear to be controlled by extension-related, 

low-angle fault scarps that expose deeper, older sedimentary 

strata within the inner wall of the trench (Torres and others, 

1996a). Within the block-faulted transform margin extending offshore southern California, massive barite deposits are 

forming where permeable strata of the San Clemente Basin 

are exposed along the San Clemente Fault zone (Torres and 

others, 2002). Farther north along this transform boundary, 

the setting of cold seeps and barite deposits in Monterey 

Canyon suggests that discharge was triggered by slope failure resulting from seismic activity (Naehr and others, 2000). 

In these occurrences, tectonic events may permit the sudden 

transfer of Ba-rich fluids and diagenetic fronts to the sediment-water interface.

The thermal history of cold seeps is an unresolved 

issue. The question arises as to whether cold seeps in some 

regions may represent the surface manifestations of warmer 

(hydrothermal) fluids at depth. For example, studies of barite 

deposits from the same area of the Peru margin have resulted 

in two interpretations: (1) the deposits are diagenetic and 

formed during discharge of cold, reduced, Ba-rich fluids 

(Torres and others, 1996a); or (2) the deposits formed at elevated temperatures (max 80°C) from deeply circulating hightemperature brines (Aquilina and others, 1997). Similarly, 

barite deposits along the San Clemente Fault in the southern 

California Continental Borderland have been interpreted as 

cold-seep deposits on the basis of the absence of temperature 

anomalies (Torres and others, 1996b), and as hydrothermal 

deposits on the basis of geologic and heat-flow relations 

(Lonsdale, 1979). Hein (2002) also suggested a hydrothermal 

origin for barite deposits recovered in the California Continental Borderland. These divergent interpretations of barite 

formation suggest that two types of fluid might circulate 

along fault zones in active-margin settings: (1) relatively 

shallow formation waters whose composition is controlled 

by sulfate reduction in the sediment; and (2) warmer, deeply 

circulating fluids driven by heat sources intersected by faults 

at depth. Seismic events are likely to promote circulation to 

greater depths within the crust of fluids that subsequently 

vent as either warm or cool fluids along the surface expression of the fault. Barite can precipitate from reduced fluids 

of either type upon mixing with ocean water at or below the 

sea floor.

 Modern Ocean-Floor Barite Deposits
12 Contributions to Industrial-Minerals Research

Hydrothermal Barite Deposits

Hydrothermal barite deposits are presently forming in 

various tectonic settings around the Pacific Ocean, including 

midocean and backarc spreading centers, volcanic arcs, fracture zones, and block-faulted transform continental margins 

(fig. 5; table 1). Barite-dominant and massive barite deposits 

are known to occur in several hydrothermally active, sediment-rich environments near continental margins: (1) in the 

Escanaba Trough, the southernmost spreading axis of the 

Gorda Ridge; (2) in Guaymas Basin, a spreading segment in 

the Gulf of California, (3) at several sites in the California 

Continental Borderland offshore southern California, and (4) 

in a pullapart basin in the Blanco Fracture Zone, a transform 

fault that connects the Gorda and Juan de Fuca spreading axes 

in the northeastern Pacific Ocean. These hydrothermal deposits are related to fluid circulation, volcanism, and emplacement of magma bodies at depth.

In the Escanaba Trough and the Guaymas Basin, massive 

sulfide and sulfate deposits are present where hydrothermal 

fluids circulating through several hundred meters of silt and 

sand turbidites vent onto the sea floor (Koski and others, 

1985, 1988; Zierenberg and others, 1993). In each place, the 

heat source driving fluid circulation is a mafic sill complex 

emplaced near the base of the sedimentary sequence. Similar 

to those on sediment-free ocean ridges, active hydrothermal 

vents at sediment-covered spreading centers are inhabited by 

vent faunas, including tubeworms. In the Escanaba Trough, 

massive barite (>50 weight percent BaSO4) occurs as (1) 

coalesced chimney edifices above sulfide mounds (fig. 8D), 

(2) isolated columnar chimneys on sediment substrate (fig. 

8E), and (3) crusts on sulfide-dominant mounds. The BaSO4

content of the sulfate-rich hydrothermal deposits varies. 

Chimneys consist of spongy, nearly monomineralic aggregates of euhedral barite crystals, whereas sinters are mixtures 

of coarse-grained (tabular crystals, max 2 cm across) barite, 

pyrrhotite, sphalerite, and galena. Amorphous silica is also 

present in some crust samples.

Similar barite-rich samples mixed with trace to minor 

amounts of sulfides have been recovered from active vent 

fields in the Guaymas Basin (Peter and Scott, 1988, 1991). 

Most of the barite-rich samples are from chimneys, but a 

dredged sample of massive granular barite interlayered with 

compact diatomaceous mud was described by Koski and 

others (1985). Although the temperature of formation of massive barite deposits has not been determined on the sea floor, 

O-isotopic data on barite samples from the Guaymas Basin 

and measurements of sulfate-depositing fluids in the Escanaba 

Trough suggest a range of about 200–225°C (Koski and 

others, 1985; Zierenberg and others, 1993).

Within the East Blanco Depression, an extensional basin 

near the west end of the Blanco Fracture Zone, barite-rich 

deposits occur on the sediment-covered margins of a pillowlava dome (Hein and others, 1999). The hydrothermal-vent 

field, approximately 70 by 90 m, is underlain by volcaniclastic and biosiliceous sediment. Small (<5 m high) mounds and 

chimneys and thin (<10 cm thick) beds dominated by barite 

and silica have formed during diffuse flow of low- to intermediate-temperature hydrothermal fluids (<250°C) through the 

volcanic and sedimentary deposits.

All of the barite-rich deposits in sediment-covered oceanridge environments are spatially related to sulfide mineralization. Samples of massive barite from the Escanaba Trough, 

the Guaymas Basin, and the Blanco Fracture Zone also contain small to significant amounts of Fe, Mn, Zn, Pb, Ag, Au, 

and SiO2. Bulk analysis of a sample of nearly pure barite from 

a chimney in the Escanaba Trough indicates that the barite 

contains approximately 2.0 weight percent Sr (Koski and 

others, 1994), whereas the measured Sr content of barite from 

the Guaymas Basin ranges from 0.7 to 2.6 weight percent 

(Peter and Scott, 1991). S-isotopic analyses of hydrothermal 

barite from the Escanaba Trough (δ34S=20.4–22.6 permil) 

and the Guyamas Basin (δ34S=23.1–29.3 permil) indicate 

that much of the sulfur in barite is derived from present-day 

seawater (δ34S∼21 permil) during mixing with hydrothermal 

fluids (Peter and Shanks, 1992; Zierenberg and others, 1993; 

Paytan and others, 2002). The higher δ34S values (>23 permil) 

of hydrothermal barite from the Guaymas Basin, however, 

indicate some sulfate reduction during the mixing process. 

This fractionation could occur as isotopically lighter sulfur is 

preferentially incorporated into sulfide minerals, resulting in 

34S-enriched hydrothermal fluid for sulfate precipitation (Peter 

and Shanks, 1992).

Sr-isotopic data for hydrothermal barite from the Guaymas Basin and Middle Valley, a sediment-covered, hydrothermal-vent field on the northern Juan de Fuca Ridge, were 

reported by Paytan and others (2002) and Goodfellow and 

Franklin (1993), respectively. At each site, 87Sr/86Sr ratios 

for barite cluster near 0.706, values that are approximately 

midway between those of modern seawater (~ 0.709) and 

ocean-ridge basalt (~ 0.703). These ratios are probably 

derived from interaction between nonradiogenic hydrothermal 

fluids (ratios close to those of oceanic crust) and underlying 

terrigenous sediment that contains more radiogenic strontium. 

The Sr-isotopic ratios of hydrothermal barite are, however, 

low relative to diagenetic barite, which has ratios closer to 

that of sulfate in ambient seawater (Paytan and others, 2002).

Another setting for sea-floor hydrothermal barite mineralization is the offshore California Continental Borderland 

(fig. 5). The basement rocks of this submerged and predominantly transform continental margin consist of Mesozoic and 

Tertiary volcanic and sedimentary rocks that are overlain by 

diverse sedimentary strata of marine origin (Vedder, 1987). 

The ridge-and-basin topography of the borderland resulted 

from both transtensional and transpressional stresses active 

during an extended period of wrench faulting from mid-Tertiary time to the present. In places, a combination of extension, block faulting, and high heat flow within the borderland 

may result in conditions favorable for hydrothermal activity 

and the formation of barite deposits.

Massive barite nodules and slabs, considered to be 

hydrothermal in origin, were dredged from the ocean floor 

offshore California (Revelle and Emery, 1951; Goldberg and 

others, 1969; Cortecci and Longinelli, 1972). At a site near 
13

the base of a scarp within the San Clemente Fault zone, cone 

and moundlike deposits of massive barite, approximately 

2 to 3 m high (and one deposit 10 m high), at apparently 

active ventsites were observed over a lateral distance of 

100 m during submersible investigations (Lonsdale, 1979). 

Although no temperature data were collected, Lonsdale proposed that the presence of vestimentiferan tubeworms and 

the milky appearance of bottom water near the deposits are 

evidence for a hot-spring environment and hydrothermal 

deposition of barite.

A more extensive, submersible-based study of fluid flow 

along the San Clemente Fault scarp has called into question the hydrothermal origin of massive barite deposits in 

the California Continental Borderland (Torres and others, 

2002). Torres and others (2002) detected no temperature 

anomalies in fluids emanating from sand and mud turbidites 

exposed on the fault scarp and proposed a cold-seep origin 

for barite in this setting. A possible hydrothermal origin (that 

is, from heated fluids present at depth) for the San Clemente 

barite deposits cannot be ruled out solely on the basis of 

their reported physical and chemical characteristics. The 

barite samples collected by Lonsdale (1979) and Torres and 

others (2002) are porous and massive (>92 weight percent 

BaSO4) and contain as much as 3 weight percent Sr. Their 87Sr/86Sr ratios near 0.7084 (Paytan and others, 2002; Torres 

and others, 2002) reflect previous interaction of the vent fluid 

with rocks less radiogenic than seawater; δ34S values of 22.1 

to 24.6 permil (Paytan and others, 2002) are similar to those 

for hydrothermal barite from the Escanaba Trough and the 

Guaymas Basin. No sulfide mineralization has been reported 

in association with the barite deposits along the San Clemente 

Fault zone.

Other massive barite deposits collected from four 

dredges elsewhere in the California Continental Borderland 

are texturally and isotopically distinct (Hein, 2002). The 

samples were recovered from sites along strike-slip and 

basin-margin faults to 1,800-m depth. The dredged samples 

include both porous, vuggy aggregates and massive veinlike 

deposits of nearly pure barite (94–98 weight percent BaSO4); 

some of the vuggy samples contain embedded worm tubes, 

as much as 10 cm long (fig. 8F). Chemical analyses of the 

massive barite also show low total rare-earth-element (REE) 

contents (<45 ppm), Sr contents of as much as 10,000 ppm, 

and Hg contents of as much as 1 ppm. Shale-normalized 

REE patterns show light-REE enrichments and large positive Eu anomalies characteristic of marine hydrothermal 

fluids. δ34S values range from that of seawater (21 permil) to 

high values (67.4 permil). High S-isotopic ratios are probably caused by Rayleigh fractionation during closed-system, 

bacterial sulfate reduction in a methane- or hydrocarbon-rich 

environment below the sea floor (Hein, 2002). The barite 

samples with near-seawater δ34S values are vuggy material 

believed to have formed on or immediately below the sea 

floor. The dredged barite vein samples have textures and 

δ34S values similar to those of the massive barite veins, as 

much as 1 m wide, that are exposed in seacliffs of the nearby 

Palos Verdes headlands (Hein, 2002). The occurrence and 

composition of this type of massive barite deposit suggests 

that reduced, Ba-rich hydrothermal fluids may circulate and 

deposit barite at depth along faults zones. The vast California 

Continental Borderland is a tectonically complex region that 

may contain both cold-seep and hydrothermal barite deposits 

in close proximity to one another.

Modern Marine Barite Deposits as 

Analogs of Stratiform Barite Deposits 

in Nevada: A Starting Point

Strict analogs for the Paleozoic stratiform barite deposits of Nevada may be absent in modern ocean basins. The 

absence of stratification and the relative scarcity of anoxic 

bottom waters at present preclude the widespread “bathtub 

ring” deposition of barite where oxic/anoxic seawater boundaries intersect the walls of closed basins or escarpments. In 

contrast, marine anoxia was intermittently widespread during 

the Paleozoic, especially during Late Devonian time (for 

example, Joachimski and Buggisch, 1993; Chen Daizhao and 

Tucker, 2003), a period during which black shale, stratiform 

barite, and sediment-hosted Pb-Zn deposits formed along the 

continental margin of North America (Goodfellow and Jonasson, 1984; Turner, 1992a). Despite this cautionary note, a 

“modern analogs” approach can provide valuable insights into 

the origin of stratiform barite deposits in Nevada and elsewhere. This section summarizes relevant observations regarding barite mineralization in tectonic settings of the Pacific 

Basin and offers suggestions for future research.

Tectonic Setting

Several sediment-rich tectonic settings around the Pacific 

rim contain massive barite deposits (fig. 5), and one or more 

of these types of setting may have been present along the 

western margin of North America during the Paleozoic. 

Potential tectonic analogs for stratiform barite deposits in 

a sediment-rich environment include ocean ridges in close 

proximity to (Escanaba Trough) or intersecting (Guaymas 

Basin) the continental margin, marginal basins (Sea of 

Okhotsk), convergent margins (Peru), and transform margins 

(California Continental Borderland). At present, none of these 

settings can be ruled out as an analog for ancient stratiform 

barite of the Roberts Mountains Allochthon, although oceanridge settings are less likely because ophiolitic rocks are 

absent in the allochthon and all known present-day hydrothermal systems at ocean ridges have spatially related sulfide 

mineralization and mafic igneous rocks related to sea-floor 

spreading.

Barite deposition in a rifted-continental-margin setting 

such as the Guaymas Basin and in a marginal-basin setting 

such as the Sea of Okhotsk is consistent with the models for 

rifting and barite metallogenesis along continental margins 

described by Maynard and Okita (1991) and Madrid and 

Modern Marine Barite Deposits as Analogs of Stratiform Barite Deposits in Nevada: A Starting Point
14 Contributions to Industrial-Minerals Research

others (1992) in which extension develops on a platform of 

continental crust. Again, however, these contemporary settings may contain igneous-rock suites derived from extensive 

rifting that are absent in the stratigraphy of the Paleozoic 

margin assemblages in the Roberts Mountains Allochthon. 

The convergent-margin setting offshore Peru and the transform-margin setting offshore California may have had tectonic equivalents in the long-lived active margin of western 

North America during Paleozoic time. Though not fundamentally extensional, these types of plate boundary contain 

tensional and transtensional zones manifested by block faulting and the creation of pathways for fluid circulation and discharge onto the sea floor.

Other occurrences of marine barite are known in sediment-floored, oceanic tectonic settings not discussed in this 

chapter—for example, hydrothermal barite in pullapart basins 

of the Blanco Fracture Zone (fig. 5; Hein and others, 1999) 

and diagenetic barite on the continental slope of the Gulf of 

Mexico, a passive-margin site (fig. 5; Fu and others, 1994). 

As these sites become better known, their significance within 

a “modern analogs” approach should be evaluated.

Depositional Processes

The accumulation rate of particulate barite from biogenic 

or hydrothermal sources seems inadequate to form massive 

deposits in modern ocean basins. The constant rain of barite 

from the water column is, however, an important component 

of the barium cycle in the oceans and must contribute to the 

Ba content of sediment or pore fluids that can be subsequently 

concentrated by diagenetic or hydrothermal processes.

Massive barite deposits of sufficient size to warrant comparison with Nevada deposits are presently forming in sediment-dominated environments on the ocean floor. Diagenetic 

and hydrothermal deposit types are characterized by similar 

sedimentary associations (fine-grained turbidites and biosiliceous sediment) and vent-specific biologic communities. The 

barite deposits formed along sub-sea-floor “diagenetic fronts” 

(Torres and others, 1996b) may have analogs in Paleozoic 

sedimentary sequences but appear to lack the volume and 

purity of stratiform barites. Similarly, well-studied sedimenthosted hydrothermal barite deposits on ocean ridges lack the 

continuity and volume of ancient deposits; the modern deposits generally represent sulfate “facies” within larger sulfidedominant mineral systems. In addition, the less radiogenic 

87Sr/86Sr ratios of modern deposits on sediment-covered rift 

zones, a reflection of Sr input from basaltic crustal sources, 

contrasts with the Sr-isotopic ratios of ancient deposits.

Cold-seep barite deposits appear to have attributes (size, 

distribution along fault scarps), mineralogy (BaSO4 content, 

SiO2 content), and isotopic characteristics (S, Sr) that, in 

total, more closely resemble those of the stratiform deposits 

of Nevada. The siliceous and organic-rich sediment related to 

high-productivity zones in the Sea of Okhotsk, along the Peru 

margin, and in the California Continental Borderland is reminiscent of the organic-rich chert and shale associated with 

barite deposits in the Roberts Mountains Allochthon. These 

high-productivity zones represent a favorable environment 

for bacterially mediated sulfate reduction leading to the 34Senriched isotopic signature of diagenetic barite.

Working Hypothesis and Avenues for Future 

Research

A consideration of the stratiform barite deposits of 

Nevada and the submarine barite deposits along modern 

continental margins yields a working hypothesis for the most 

suitable modern analog. Our study suggests that cold-seep 

mineralization in tensional environments along modern 

transform continental margins (or, possibly, marginal basins) 

represents a process and setting most likely to accumulate 

large deposits comparable to the stratiform barite deposits of 

Nevada. Hydrothermal systems can also accumulate highgrade barite, but the small scale of such deposits presently 

known on the modern sea floor and the paucity of sulfide 

mineralization in the ancient deposits are problematic. At 

this point, neither the presence of vent faunas nor S-isotopic 

data for barite permit discrimination between a diagenetic or 

hydrothermal origin. Interpretation of the genesis of barite 

deposits may be complicated by the juxtaposition of hydrothermal and diagenetic deposits in the same tectonic setting 

(for example, the California Continental Borderland).

This chapter is based on a review of available data; 

clearly, acquisition of new data is needed to facilitate comparisons between modern and ancient barite deposits and 

among deposit types, to identify the most likely analogs in 

the modern ocean, and to apply what is known about these 

analogs to the construction of better deposit models for 

stratiform barite. We note that two recent parallel studies 

have resulted in similar conclusions regarding (1) cold-seep 

environments as likely depositional analogs (Torres and 

others, 2003) and (2) the California Continental Borderland as a probable tectonic analog (Clark and others, 2004) 

for Nevada barite deposits. Suggested areas of additional 

research include:

1. Detailed geochemical, isotopic, and paleontologic studies 

of ancient stratiform barite deposits to identify additional 

genetic indicators. In addition, further regional site-specific 

petrologic studies in the Roberts Mountains Allochthon 

are needed to better understand the tectonic framework for 

sedimentary rocks and contained barite deposits.

2. Additional detailed investigations of fluid flow and mineralization along modern transtensional continental margins 

(including marginal basins) to elucidate ore-forming 

processes. These investigations should be conducted in 

conjunction with future submersible and drilling programs 

in the ocean basins.

3. Additional analytical data for both modern and ancient 

barite deposits to augment the data listed in table 1, including trace elements, REEs, and Pb, Sr, C, and O isotopes 

for barite and associated minerals. Geochemical and isotopic characterization of modern marine barite deposits 
15

by Paytan and others (2002) indicates the value of this 

approach.

4. Further studies of the fluid chemistry of cold seeps to determine whether hydrothermal processes contribute to mass 

flux at the ventsites.

Acknowledgments

We thank Bonnie Murchey, Don Singer, and George 

Havach for their careful reviews of the manuscript.

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